1. Magnetic Configuration of the Muon Collider/ Neutrino Factory Target System Hisham Kamal Sayed, *1 H.G Kirk, 1 K.T. McDonald 2 1 Brookhaven National Laboratory, Upton, NY 11953 2 Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 *Email: hsayed@bnl.gov Work supported in part by US DOE Contract No. DE-AC02-98CH10886. Abstract An alternative capture-solenoid field is presented for the mercury jet target for a neutrino factory or muon collider. A peak solenoid field of 15 T at the mercury-target location is studied in comparison to the current baseline value of 20 T. The magnetic-field profile tapers down to 1.5 T in the Front End, nominally beginning 15 m downstream of the target. This field profile is optimized to maximize the “useful” muons 50 m downstream from the target within a kinetic-energy window of 80-140 MeV. Two parameters are considered for the optimization study: the length z end of the tapered field and the field strength in the front end. The axial-magnetic-field profile is specified analytically using an inverse-cubic equation and the off-axis field is computed from a series expansion based on derivatives of the axial field. The simulation is performed using the MARS15 code.  Mercury-Target Parameters  Angle of target to solenoid axis θ target = 0.137 rad  Target radius r target = 0.404 cm  Proton Beam Parameters  E = 8 GeV  θ beam = 0.117 rad  σ x = σ y = 0.1212 cm (Gaussian distribution)  Solenoid Field  20 T peak field at target position (z = -37.5 cm)  Aperture at Target, r = 7.5 cm,  Aperture at Front End, r = 30 cm  z end = 1500 cm, where B z =1.5 T  Muons within kinetic-energy cut of 40-180 MeV  N muons at z = 50 m = 3.27  10 4 (N initial protons = 10 5 ) Mercury Target – Proton Jet Baseline Parameters (from optimization by X. Ding using MARS15)  Particle-capture requirement (P t ≤ 0.225 GeV/c)  B × r = 20 T × 7.5 cm = 150 T-cm  B × r = 15 T × 10 cm = 150 T-cm  Fixed-flux requirement (Aperture requirement)  B × r 2 = 20 × 7.5 2 = 1125 T-cm 2  B × r 2 = 15 × 10 2 = 1500 T-cm 2  MARS simulations with 15-T peak field & new aperture settings (taper radius r = 30 cm at all z) Analytic Form for Tapered Solenoid Inverse-Cubic Taper, defined by initial & final axial fields (B 1 & B 2 ), their derivatives, and position of end of taper (z end ): Off-axis field approximation:  Beam Pipe with constant r = 30 cm.  Beam Pipe material changed to “MARS-Blackhole” to speed calculation.  Added subroutine to m1510.f (FIELD) to calculate the field an using inverse-cubic fit. RESULTS Muon count at 50 m for kinetic energy within 80-140 MeV: Tapered field using inverse-cubic field (P = 1) Conclusion Muon Production IDS120h 15 T MARS 1510 Simulation Setup  Promising results for 15-T peak field at the target, particularly if increase z end beyond 15 m and the Front-End magnetic field above the 1.5-T baseline.  To be done:  Investigate transmission through the downstream phase rotator & cooling sections, using ICOOL. Hg jet Proton beam θ Beam θ Target Solenoid axis Hg jet Proton Beam B z (z=0,r=0) = 15 T Beam Pipe B z [T] z [cm] r [cm] z end [cm] B z [T] z [cm] r [cm] IDS120h (R. Weggel) B z (r=0) = 15 T